This invention relates to the fusion bonding of articles constructed of plastic, and more particularly to boring a fill opening in a molded plastic container or other workpiece, and forming a fusion bond between a plastic fill spout and a rim portion about the bore.
Fusion bonding, also known as hot plate welding, is a well known technique for establishing strong bonds between plastic members. Generally, the articles to be bonded are positioned spaced apart from one another with the surface portions to be bonded aligned and facing one another. A heating plate then is interposed between the articles and in contact with the surfaces to be bonded in order to form a fused or plasticized layer of the plastic comprising the articles. Immediately after heating, the platen is withdrawn and the articles are brought together under pressure and allowed to cool to form the bond.
This application is concerned with a particular application of the fusion bonding process, namely the attachment of a tubular spout to a container, for example a gas tank in which the spout is to be employed as a filler spout for the tank. It has been found feasible to form a bore in a container by drilling, then securing the spout to the container in a rim area about the bore. This approach, however, is subject to certain difficulties. Foremost among these is contamination in the form of plastic chips or shavings deposited into the container in the course of machine-forming the bore. Such contamination can cause damage to a vehicle when the container is to be used as a gasoline tank. Alternatively, the shavings and chips give rise to an additional manufacturing step of cleaning the container, which adds to manufacturing time and cost while not assuring complete removal of fragments.
Further, as machine-forming of bores typically involves drill bits or other rotating cutting tools, the profile of the bore typically must be circular. Machine-forming of the bore is accomplished independently of the fusion process, and thus an intermediate spout alignment step is required for the desired positioning of the spout with respect to the container.
Among various known fusion bonding techniques are a few which involve forming openings or bores substantially contemporaneously with fusing. For example, U.S. Pat. No. 3,075,573 (Piazze) shows a system for punching cutouts in sheets of thermoplastic film material, and bonding the sheets together in the areas surrounding the cutouts. A heated dye is employed to form the bore and the fusion bond in a single operation. The pair of sheets to be bonded are pre-aligned, in the sense that the sheets are contiguous during the operation. A process for forming bores in plastic molded parts is disclosed in U.S. Pat. No. 3,501,618 (Spranger). An electrode is pressed into a plastic article, and a high voltage arc is formed in the plastic article between that electrode and another while a stream of gas is passed in the spark gap between the electrodes. While the above techniques are satisfactory in certain respects, they fail to adequately address needs particular to fusion bonding plastic spouts and containers and forming the required bores in such containers.
Therefore, it is an object of the present invention to provide an apparatus for forming a bore through a wall of a container without forming chips, shavings and the like, and for fusing a rim portion about the bore and a corresponding end portion of a tubular spout to be joined to the container at the rim portion.
Another object of the invention is to provide a fusion bonding apparatus that facilitates alignment of a bore formed in a plastic container and a spout to be joined to the container about the bore, and further permits the selection of a wide variety of profiles for the bore and spout.
Yet another object is to provide a process for forming a bore through the wall of a molded plastic container, without depositing chips, shavings or other plastic fragments in the container, and for aligning and fusion bonding an end of the spout to a container rim area about the bore.